Chromosome pulverization in human binucleate cells following colcemid treatment.

Under the influence of Colcemid, a substantial number of binucleate human cells from a line infected with herpes-like virus was found to possess pulverized chromosomes. Although this abnormality was also detected in untreated binucleate cells, the increase in the number of pulverized cells after the addition of Colcemid was too striking to be explained by accumulation of spontaneously occurring cells in response to the mitotic inhibition by Colcemid. Furthermore, the induction of pulverization may be dependent upon Colcemid concentration. These findings imply an involvement of Colcemid in the mechanism of pulverization induction in the system studied. When tritiated thymidine was added to the culture medium simultaneously with Colcemid, the majority of binucleate cells with an intact and a pulverized chromosome set incorporated this isotope into the pulverized set only. This obviously suggests that the nuclei in the binucleate cell are asynchronous in DNA synthesis, and that this asynchrony is intimately related to the induction of the pulverization phenomenon. It seems very probable that the late S phase in the late synthesizing nuclei represents a critical stage at which damage to the chromosomes most readily occurs.

Quantitative conservation of chromatin-bound RNA polymerases I and II in mitosis. Implications for chromosome structure.

RNA synthesis almost ceases in mitosis. It is ambiguous whether this temporal, negative control of RNA synthesis is solely because of the nature of chromosomes per se, (i.e., their condensed state), or to a physical loss of RNA polymerases along with other nuclear proteins which have been shown to pass into the cytoplasm in mitosis, or to their combined feature. Aside from such regulatory considerations, a question has also been raised as to whether RNA polymerases are constituents of metaphase chromosomes. To clarify these aspects of RNA polymerase-chromatin interaction in mitosis, the enzymes in chromosomes were quantitated and their levels compared to those in interphase nuclei and cells at various phases of the cell cycle. The results show that the amounts of form I, form II, and probably form III enzymes bound to a genome-equivalent of chromatin stay constant during the cell cycle. Thus, the mechanism for the negative control of RNA synthesis in mitosis appears to exist in the chromosomes per se, but not to be directly related to the RNA polymerase levels. This quantitative conservation of chromatin-bound RNA polymerases implies that they may persist as structural components of the chromosomes in mitosis.

Detection by means of cell fusion of macromolecular synthesis involved in the reconstruction of the nuclear envelope in mitosis.

Using the cultured Chinese hamster cell line Don, G1 or S or a mixture of late-S/G2 cells were prepared by release from metaphase arrest. Metaphase (M) cells were also obtained by mitotic arrest of log-phase cultures with Colcemid and held in metaphase; such M cells remained untreated with any other compound and were termed standard M cells. When interphase (I) cells were fused at pH 8.0 and 37 degrees C with standard cells in the presence of Colcemid by means of UV-inactivated Sendai virus, binucleate interphase-metaphase (I-M) cells were obtained. In a given I-M cell there occurred within 30 min after fusion either prophasing of the I nucleus or formation of a nuclear envelope (NE) around the chromosomes. About 20% of early G1 cells, 35% of cells at the G1/S boundary, 50% of S cells, and 70% of late S/G2 cells could induce NE formation. If, before fusion, cycloheximide (CHE), an inhibitor of protein synthesis, was present during release from M arrest, the cells entered G1 but not S. About 20% of such early G1 cells, like the untreated early G1 cells, had the capacity to induce NE formation during subsequent fusion. If the cells were blocked in S with 5 mM thymidine (TdR), At least 80% of these cells could induce NE formation during subsequent fusion, but in the presence of both TdR and CHE only 35% could do so. It appeared, therefore, that protein synthesis in interphase was required for NE formation. Experiments with actinomycin D indicated that RNA synthesis was also necessary for acquisition of NE-inducing capacity. About 35% of G1 cells from confluent monolayers had the NE-inducing capacity, but prolonged exposure to CHE reduced their number to 8% . Removal of CHE restored the ability while the cells still remained in G1. This result indicated that continuing protein synthesis in the G1 cell was needed for NE formation subsequent to fusion. The fact that macromolecular synthesis must occur in the I cell before fusion if NE formation was to occur in the fused I-M cell lends further support to evidence adduced earlier that this phenomenon is a normal mitotic event. Prophasing of the I nucleus in I-M cells did not appear to be dependent on macromolecular synthesis in the I cell; earlier results from this laboratory showed, however, that protein synthesis in the prior G2 period of the M cell of the I-M pair was required for prophasing.

Chromosome pulverization in micronuclei induced by tritiated thymidine.

Cultures of a pseudodiploid cell line (Don) of Chinese hamster origin were exposed to varying doses of tritiated thymidine (TdR-(3)H) for relatively long periods of time. In addition to previously observed chromosomal aberrations) such as breaks and reunions, a substantial number of interphasic cells with micronuclei and of metaphases associated with pulverized chromosomes was found; both phenomena were dependent on exposure time to and concentration of TdR-(3)H. The former phenomenon appeared to result from the effects of the beta-emissions originating in the TdR-(3)H. A possible interpretation for chromosome pulverization induction is presented, emphasizing the derivation of the pulverized material from micronuclei in a common cytoplasm with a metaphase nucleus. These observations further substantiate our previously advanced hypothesis regarding the essential role played by substances present in a mitotic cell in the induction of chromosome pulverization and nuclear membrane dissolution.

Induction of nuclear envelopes around metaphase chromosomes after fusion with interphase cells.

The process of cellular fusion induced by Sendai virus in Chinese hamster cells (Don line) afforded us the opportunity to study nuclear envelope formation around metaphase sets in the presence of interphase nuclei, when chromosome pulverization failed to occur in such multinucleate cells. Morphologically, the enveloped metaphase chromosomes resembled a normal telophase nucleus, though minor differences prompted us to call it telophase-like. Electron microscopic observations demonstrated that the membranes enveloping the chromosomes appeared to be identical with a normal nuclear envelope. The longer the cells were incubated with Colcemid before fusion, the higher was the number of cells with telophase-like nuclei and the lower the percentage of cells with pulverizations. Furthermore, the number of pulverizations bore a somewhat direct relationship to the ratio of metaphase to interphase nuclei in multinucleate cells, and the number of telophase-like nuclei was inversely proportional to this ratio. A hypothesis is advanced in which a balance between the activities of a chromosome pulverization factor and a nuclear envelope formation factor, the former in metaphase cells and the latter in interphase cells, is decisive as to the nature of morphologic events observed in virus-induced fused cells.

Induction of prophase in interphase nuclei by fusion with metaphase cells.

Fusion of an interphase cell with a metaphase cell results in profound changes in the interphase chromatin that have been called "chromosome pulverization" or "premature chromosome condensation" In addition to the usual light microscopy, the nature of the changes has been investigated in the present study with electron microscopy and biochemical techniques Metaphase and interphase cells were mixed and fused at 37 degrees C by means of ultraviolet-inactivated Sendai virus. After cell fusion, morphological changes in interphase nuclei occurred only in binucleate cells which contained one intact set of metaphase chromosomes Irrespective of the nuclear stage at the time of cell fusion, the morphologic changes that occurred 5-20 min later simulated very closely a sequence of events that characterizes the normal G(2)-prophase transition. Radioautography revealed that, late in the process, substantial amounts of RNA and probably protein were transferred from the interphase nucleus into the cytoplasm of fused cells. Thus, the findings indicate the existence in metaphase cells of factor(s) which are capable of initiating biochemical and morphological events in interphase nuclei intrinsic to the normal mitotic process.

Prophasing of interphase nuclei and induction of nuclear envelopes around metaphase chromosomes in HeLa and Chinese hamster homo- and heterokaryons.

Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6-8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.

Contrast between the environmental pH dependencies of prophasing and nuclear membrane formation in interphase-metaphase cells.

In Chinese hamster Don cells, fusion of an interphase cell with a metaphase cell resulted either in prophasing of the interphase nucleus, including loss of the nuclear envelope (NE), or in the formation of a double membrane around the metaphase chromosomes. Only one of these phenomena occurred in a given interphase-metaphase (I-M) binucleate cell. At pH 7.4, there was about an equal probability that either event could occur amongst the population of I-M cells. The effect of pH changes in the medium containing the fused cells was examined. At pH 6.6, prophasing was the predominant event; at pH 8.0, membrane formation predominated. It was found that the rate of progression of a mononucleate cell from G(2) to metaphase was appreciably faster at pH 6.6 than at pH 8.0. Conversely, the progression from metaphase to G(1) was faster at pH 8.0 than at pH 6.6. These results with the mononucleate cells strengthen the hypothesis that structural changes in I-M cells are reflections of normal mitotic phenomena. Additional evidence for this hypothesis was produced by electron microscope examination after direct fixation in chrom-osmium. The double membrane around the chromosomes of the I-M cell was indistinguishable from the normal NE. The results obtained by varying the pH of the medium containing the fused cells provide an indication that disruption or formation of the NE of Don cells depends on the balance reached between disruptive and formative processes.

Normalization by cell fusion of sister chromatid exchange in Bloom syndrome lymphocytes.

Fusion of fresh lymphocytes from a Bloom syndrome (BS) patient with those of normal subjects or a BS heterozygote resulted in complete normalization of the frequency of sister chromatid exchanges in the chromosomes of BS cells. This normalization took place by the first mitosis in hybrid cells. In contrast, cultivation of BS lymphocytes with those of normal subjects or the BS heterozygote had no effect on sister chromatid exchanges. The cell fusion experiments suggest that the normalization on the sister chromatid exchanges. The cell fusion experiments suggest that the normalization of the sister chromatid exchange frequencies in BS cells can be achieved by factors conserved in the cells of various mammalian species. These findings are compatible with the concept that BS is a recessive genetic mutation at regulatory levels of the DNA repair function.

Studies on phenolic steroids in human subjects. 8. Metabolism of estriol-16 alpha-glucosiduronate.

6,7-(3)H-Estriol-16alpha-glucosiduronate-(14)C was administered to eight women (nine studies) by several routes: both injection and infusion (300 min) into the cubital vein, injection into the portal vein system, ingestion and instillation into the duodenum, jejunum, and ileum. Urine, collected from 0-2, 2-4, 4-8, 8-12, and 12-24 hr, was analyzed by countercurrent distribution for its content of radioactive 3- and 16-glucosiduronate (E(3)-3Gl,E(3)-16Gl) and sulfoglucosiduronate (E(3)-3S,16Gl) of estriol as well as for (3)H/(14)C ratio of each conjugate. After peripheral injection 50-60% of the injected E(3)-16Gl was excreted unchanged along with about 5% as E(3)-3S,16Gl with an unchanged (3)H/(14)C ratio, indicating direct sulfation of the injected E(3)-16Gl. During a 300 min infusion, urinary excretion closely resembled that following injection. But 2-4 hr after the end of the infusion excretion of E(3)-3S, 16Gl stopped, excretion of E(3)-3Gl (17%/24 hr) with an elevated (3)H/(14)C ratio started, and excretion of E(3)-16Gl continued (70%/24 hr), but with a rapidly increasing (3)H/(14)C ratio. This indicated sequestration in a sluggishly metabolizing compartment where two processes occurred: (a) extensive hydrolysis of E(3)-16Gl followed by reconjugation at either C3 or C16 with unlabeled uridine diphosphate glucuronic acid (UDPGA), thereby increasing the (3)H/(14)C ratio; and (b) transconjugation from C16 to C3, thereby producing E(3)-3Gl with finite (3)H/(14)C ratios. Instillation into various segments of the small intestine produced results qualitatively similar to those after intravenous infusion, whereas ingestion and intraportal injection resembled peripheral intravenous injection. Therefore, we have postulated the possibility of an enteric circulation (in addition to an enterohepatic circulation) in which the steroid or its conjugates are transported into the small intestine in the succus entericus, modified, and then reabsorbed and excreted in the urine-a process which requires several hours.

Studies on phenolic steroids in human subjects. IX. Role of the intestine in the conjugation of estriol.

In order to compare the enteric circulation of estriol-16alpha-glucosiduronate (see preceding paper) with that of estriol (E(3)), labeled estriol was administered to six women by several routes: both injection and infusion (300 min) into the cubital vein, injection into the portal vein system, ingestion and instillation into the jejunum and ileum. Urine, collected from 0-2, 2-4, 4-8, 8-12, and 12-24 hr, was analyzed by countercurrent distribution for its content of radioactive 3- and 16-glucosiduronate (E(3)-3Gl,E(3)-16Gl) and sulfoglucosiduronate (E(3)-3S,16Gl) of estriol. After peripheral injection of E(3), E(3)-16Gl was excreted rapidly and E(3)-3S,16Gl at a slower and more constant rate. E(3)-3Gl was barely detectable after infusion. After injection of E(3) into the portal vein, the excretion of E(3)-3S,16Gl was greater and quicker than after peripheral injection. Even in a subject with a complete bile fistula, the urinary excretion of E(3)-3S,16Gl was essentially unchanged. Ingestion also produced the same result. Only after instillation into the ileum was a large and rapid excretion of E(3)-3Gl obtained, whereas the excretion of E(3)-3S,16Gl, and E(3)-16Gl were depressed. These results together with those of the preceding paper suggest that E(3) does not readily appear in the small intestine except via a hepatoenteric circulation that produces very little E(3)-3Gl. When present in the distal segment of the small intestine, however, absorption, conjugation, and elimination proceed readily.

Chromosome pulverization in virus-induced heterokaryons of mammalian cells from different species.

The phenomena of cell fusion and chromosome pulverization after inoculation with UV-inactivated Sendai virus were studied in mixed suspensions of cell lines from different mammalian species. Two cell combinations were used: the Chinese hamster cell line (Don) and RPMI 8226 (Simpson) cell line of human hematopoietic origin,and the Don and LLC-MK2 (MK) cell lines, the latter derived from monkey kidney cells. Each of the 3 cell lines had a high cell-fusion capacity when infected with the virus in homologous cultures. The heterokaryons of Don and Simpson cells were formed at lower frequency than homokaryons in either Don or Simpson cells, and heterokaryon formation between Don and MK cells was rare. The findings indicated that the cells used maintained some specificity of the cell surfaces. Chromosome pulverization was found in heterokaryons and was similar to that observed in homokaryons. The results confirmed further our presently held concept that cell fusion is a prerequisite for induction of pulverization, and also suggest that the possible role played by the mitotic nucleus with its cytoplasm in pulverization applies to the heterologous as well as to the homologous nuclei.

A new complex Ph1 translocation involving three chromosomes.

A case of Ph1-positive chronic myelocytic leukemia associated with a complex translocation involving chromosomes No. 9, No. 17, and No. 22 was described. All cells in the marrow contained this complex karyotypic picture, and no cells with the usual type of Ph1 translocation were present. With banding analysis, the karyotypic picture consisted of 46,XX,t(9;22;17)(q34;q11;q21). The published cases of usual and complex Ph1 translocations were summarized in tabular form and some aspects of the translocations discussed.

Chromosome evolution of near-haploid clones in an established human acute lymphoblastic leukemia cell line (NALM-16).

A cell line has been established from blood lymphoblasts of a female patient with acute lymphoblastic leukemia (ALL) shown to have near-haploid (27 chromosomes) cells in the bone marrow. The findings about the cell line were: 1) The frequency of near-haploid cells in culture decreased with time from 98.2% when the culture was started to 5.4% 15 months later. 2) Most of the other cells except the near-haploid ones were hyperdiploid, i.e., duplicates of the cells with near-haploid chromosome constitutions. 3) Chromosome evolution was seen in the near-haploid clones. The possible ancestor clone (clone A) had 27 chromosomes, one of each pair except no.10, 14, 18, and 21, which were disomic. A suggested evolution process is: clone A yields clone B (26 chromosomes: clone A, -no.10) yields clone C (27 chromosomes: clone B, +X) yields clone D (26 chromosomes: clone C, -no.21), clone E (28 chromosomes: clone C, +NO.20). Clone B and D, each with 26 chromosomes, appeared to contain the lowest number of chromosomes, appeared to contain the lowest number of chromosomes ever described for human somatic cell clones in vitro. 4) Changes in the constitutions of the hyperdiploid cell clones were preceded by evolution and changes in the near-haploid clones. 5) In near-haploid cells with 2 X-chromosomes, 1 exhibited late DNA replication; in hyperdiploid cells with 3-5 X-chromosomes, 2 were non-late DNA-replicating. 6) Fresh (uncultured) and cultured leukemia cells were antigenically typical non-T, non-B or common type ALL cells (positive for la-like and null-type ALL antigens and negative for surface membrane immunoglobulin).

Suspension cell culture and in vivo and in vitro chromosome constitution of mouse leukemia L1210.

An in vitro culture of mouse leukemia L1210 was established, along with conditions for optimal growth in suspension culture. L1210 showed a high requirement for folic acid in comparison with other cell lines in vitro. As few as 10 viable cells cultured in vitro killed DBA/2 mice. Cells from ascites showed a sharp mode of 40 chromosomes, with a minute marker chromosome and an extra-small, T-type (telocentric) chromosome. Cells cultured in vitro showed a mode of 40 or 41 chromosomes and contained the minute marker but not the extra-small chromosome; in addition, an m-type (metacentric) marker chromosome was observed in the cultured cells. This in vitro system should lend itself to evaluation of karyogenesis in relation to carcinogenesis, drug effects, and cytogenetic dynamics, as well as to nutritional and metabolic studies.

Dependency of sister chromatid exchange in T- and B-cells on the incorporation of deoxyribonucleosides into chromosomal DNA.

Human T-cells (CCRF-HSB2) did not incorporate tritiated thymidine ([3H]TDR)--1.0-5.0 muCi/ml--into the nuclei, where.as they readily incorporated tritiated deoxycytidine (E13H]CDR). When contamination with pleuropneumonia-like organisms was ruled out, these findings strongly suggested a deficiency of the enzyme thymidine kinase in the cells. Human B-cells (CCRF-SB) and normal T-lymphocytes (NTL) readily incorporated [3H]CDR, [3H]TDR, and tritiated 5-bromodeoxyuridine, and they clearly exhibited differential staining of the sister chromatids (SCD). When nonisotopic bromodeoxyuridine (BUDR), 10(-6)-10(-4) M, was used with the B-cells and NTL, SCD were clearly evident and sister chromatid exchange (SCE) was relatively infrequent; when the concentration was 10(-7) M, SCD staining was poor but the frequency of SCE was high. SCE frequencies in NTL, measured by autoradiography after incorporation of [3H]CDR, were the same as SCE frequencies measured by staining with BUDR at 10(-4) M. In the case of CCRF-HSB2, 10(-4) M BUDR produced relatively high frequencies of SCE as did 10(-7) M BUDR with the former two cells. However, [3H]CDR with CCRF-HSB2 gave relatively low frequencies of SCE, of the magnitude observed after 10(-4) M BUDR was used with NTL and the B-cells. Thus the high frequency of SCE in CCRF-HSB2 cells may have been due to the staining property of chromosomes that had incorporated low levels of BUDR.

Trisomy of the long arm of chromosome No. 1 in human leukemia.

We encountered a karyotypic abnormality, i.e. a trisomy of part of or the whole long arm of chromosome No. 1, in 4 patients with leukemia; 3 with acute myeloblastic, leukemia (AML) and 1 with chronic myelocytic leukemia (CML) in the blastic phase. Q- and G-banding techniques revealed that in two patients with AML and in the one with CML, this karyotypic abnormality was not an initial one and was apparently associated with clinical progression of the disease. This chromosome change is a common karyotypic abnormality in blood disorders, especially in AML, and possibly bears a relationship to selective growth advantages of the leukemia cells.

Chromosome changes in soft tissue sarcomas.

An analysis of chromosome aberrations in human tumors was performed in 29 cases of soft tissue sarcoma. The tumor tissues were disaggregated with collagenase and the cells cultured for 2-3 days. Analyzable metaphases were obtained in 15 cases, 4 of which showed only normal karyotypes. The remaining 11 tumors showed various numerical and structural abnormalities in their karyotypes: 8 tumors were near-diploid and the remaining 3 were near-triploid. G- and Q-banding analyses revealed clonal abnormalities in the 11 cases with the presence of marker chromosomes; 15 different chromosomes were involved in chromosome rearrangements, chromosomes 1 and 2 being the most frequently affected. Because of the heterogeneity of the tumor group investigated (neurogenic sarcoma, 2 liposarcomas, neurofibrosarcoma, synovial cell sarcoma, fibrosarcoma, mesothelioma, leiomyosarcoma, rhabdomyosarcoma, Ewing's sarcoma, and hemangiopericytoma), it was impossible to reach any conclusion on the specificity of the cytogenetic abnormalities for a particular tumor type.

Cytogenetic study of a new Ph1-positive cell line (NALM-1).

The chromosomes of a cell line (NALM-1) derived from the leukocytes of a patient with chronic myelocytic leukemia (CML) were examined with several banding techniques. The modal chromosome number was 46 and the cells contained a Philadelphia chromosome (Ph1), due to the standard translocation of the missing segment of the long arm of chromosome No. 22 onto the distal end of the long arm of chromosome No. 9, i.e., t(9;22) (q34;q11). The Ph1-positive modal cells of the NALM-1 line also had two common marker chromosomes, an extra X-chromosome, and missing chromosomes in groups No. 7, 9, and 15. Immunologic examination of the NALM-1 cells revealed them to have non-T-non-B (null) surface characteristics. An antigen specific for cells of acute leukemia and a human la-like antigen were detected. These facts suggested that the NALM-1 cell line originated from CML cells and maintained the cytogenetic and Immunologic characteristics of such cells.

Chromosomes and causation of human cancer and leukemia. XX. Banding patterns of primary tumors.

Banding techniques were used in the study of the chromosomes of primary tumors from 16 patients with various types of cancer. The initial analysis with conventional Giemsa staining revealed chromosome abnormalities in 13 of the 16 tumors. Eleven of these 13 tumors and 2 of the 3 with normal karyotypes were reexamined with Q-, G-, and C-banding techniques: The 2 tumors were conventionally stained normal karyotypes were found to have no abnormalities. Nine of the tumors wre characterized by numerical changes only and 4 by both numerical and structural abnormalities. In 11 tumors, excessive chromosomes, identified with banding techniques, were usually found in the following groups (number of tumors involved is shown in parentheses): No. 5 (5), No. 8 (6), No. 11 (5), no. 13 (5), and No. 21 (5). The primary tumors examined had hyperdiploid modes; only 4 of these tumors contained marker chromosomes, as opposed to the high frequency of markers in metastatic cancer cells and the presence, usually, of high polidy (near-triploidy or near-tetraploidy). The data suggested that the karyotypic changes in primary cancers consist primarily of numerical changes (hyperploidy), rather infrequent appearance of marker chromosomes, and, when present, only 1 or 2 markers.